Anti-skid chains are usually carried unassembled in a vehicle. The anti-skid chains are only assembled and fitted to the vehicle wheels when required as a result of road conditions. The assembly and fitting, in general, takes place under conditions which are unpleasant for the user. For this reason, efforts have been made to provide anti-skid chains which can be quickly fitted to a vehicle wheel, and, in particular, can be fitted to a vehicle wheel in a relatively uncomplicated manner, so that, even in unfavorable weather conditions, an unpracticed user may assemble and fit the anti-skid chains without undue handling problems.
Many suggestions have been made in the past for providing an anti-skid chain which is more easily assembled and fitted to a vehicle wheel. Indeed, significant advances have been made in anti-skid chains in the last few years.
In known anti-skid chains, the outer side harness commonly comprises a harness line having at least one intermediately disposed elastic expansion member. One end of the harness line is connected to a locking device and the other end of the harness line is connected to a tensioning chain which passes through the locking device. A releasable locking element in the locking device releasably locks the tensioning chain in a direction opposite to the direction to which the tension force is applied to the tensioning chain for tensioning the harness line. In other words, the releasable locking element permits the tensioning chain to move freely in the direction it is pulled to apply tension to the harness line but prevents movement of the tensioning chain in the opposite direction.
In a particular known construction of anti-skid chain, the inner harness of the chain comprises an elastically expandable spring steel stirrup. A tensioning chain is secured to one free end of the stirrup which passes through a diversion eye on the other free end of the spring steel stirrup. The tenioning chain is then led from the diversion eye transversely across the tire tread to the outer side wall of the tire where its free end is suitably retained by hooking the free end to the outer side harness. The inner side harness of this known anti-skid chain may be relatively quickly assembled and fitted to the inner side of the vehicle tire by the user working from the outer side of the vehicle wheel. Besides the tensioning of the inner side harness, however, the outer side harness must likewise be tensioned in order to achieve a secure seating of the chain upon the wheel. However, in this known anti-skid chain, a once-and-for-all assembly and fitting of the chain is not possible. The chain, on being secured to the vehicle tire, must be tightened again after each journey, even if the journey is relatively short.
In another known anti-skid chain, the inner lateral harness similarly consists of a construction which can be spread apart so that it clears the tread of the vehicle. In this construction, the inner side harness comprises three or four rigid curved metal links pivotally secured to each other at their ends. The links are biased under spring forces into a closed annular shape. Closure members are mounted respectively on the two free ends of the end links. The closure members are arranged on the inner side harness so that they engage each other as the free ends of the harness come together after the expanded harness has been skipped over the tire tread and released, thereby automatically closing and locking the harness into an annular shape. A particularly rapid assembly is possible in this known anti-skid chain, since the user does not have to tighten the inner side harness from the outer side of the wheel. However, the outer side harness does have to be tightened by the user in this case.
The basic consideration, apart from rapid assembly and fitting, of an anti-skid chain onto a vehicle tire is that it is important that the chain when seated on a vehicle wheel should be well tensioned. This is necessary to ensure that the anti-skid chain functions properly. For an anti-skid chain to have good functioning properties in use, not only the static stresses but also the dynamic stresses of the chain which arise during use must be equilibrated as much as possible so that good chain seating on the tire can be maintained during use, even in the presence of the most varied stresses. Further, at the same time, the running noises of the chain which are strongly influenced by the dynamic behaviour of the chain should be held as low as possible.
It is known to provide one or more elastic expansion members in the outer side harness for tensioning the chain. The elastic expansion members are themselves tightened when the chain is tightened, and as a result of the elastic restoring force thereby generated ensure that the chain always remains tensioned on the tire even during use. This is important since, in use, alteration in the fit of the chain on the tire can arise as a result of the dynamic forces on the chain during use. This can lead to relaxation of the outer side harness.
Instead of expansion members, it is also known to use a locking device through which a tensioning chain attached to one end of the outer side harness is guided. The locking device prevents the tensioning chain (and with it the side harness which is secured to it) from running back against the direction of the tensioning force after the outer side harness has been tightened.
It is a known fact that for a considerable time now the demands which are made on modern anti-skid chains as regards the functioning properties of the chain in use and the speed with which the chain may be assembled and fitted to a vehicle tire have led to a compromise in favor of one or other of the required properties. Thus, chains with particularly good functioning properties do not lend themselves to easy and quick assembly and fitting onto a vehicle tire and vice versa.
Italian Utility Model No. 210268 discloses an anti-skid chain of the type discussed above having a tensioning arrangement for the outer side harness. The outer side harness comprises a harness line having intermediately disposed elasticity, as well as an anti-reversing locking device for a tensioning chain. In this known anti-skid chain, however, the inner side harness comprises a strong wire rope, which during assembly is first fitted to the inner side of the vehicle wheel and must have one of its ends brought around said wheel until said end once again reaches the outer side of the wheel at the other end of the vehicle wheel. It is then necessary to secure the two free ends of the wire rope to each other by a closure means which is not simple for an inexperienced user to operate. It is then necessary for the user, in order to bring the wire rope to the inner side of the vehicle wheel to form a side harness, to grasp the wire rope, closed after the securing of its ends, with both hands laterally, to pull it into an oval elongated form and to bring it upwards on the vehicle wheel, and finally to bring the upper and outer part of the wire rope across the upper tread of the vehicle tire as far as the rear side of the vehicle wheel. The assembly and tightening of the outer side harness can only be undertaken when this very awkward handling procedure of the inner side harness has been completed. In this device, the outer side harness comprises a harness line formed by a chain which has two individual sections, whose ends must be hooked together to finally produce the entire tensioning line. This hooking together of the two sections of the outer side harness can only be undertaken after the inner side harness has been brought to the inner side of the vehicle wheel. This also applies to the threading of the tensioning line through the locking device. The reason for this is that the tensioning chain must be pulled out of the locking device before the inner harness has been brought across the vehicle wheel in order to permit said transition of the inner harness. In this known anti-skid chain the tensioning chain is secured at one end of the harness line while the locking device is resiliently mounted on the other end of the harness line by a screw adjusted tension spring. The locking device comprises a releasable locking element which can be brought into engagement with the tensioning chain when the tensioning chain passes through the locking device.
While this anti-skid chain possesses good functioning properties as a result of the combination of expansion elements and tightening elements on the outer side harness, as well as by its overall construction, it is very tedious and relatively slow to assemble to a vehicle tire. For this purpose, the connections on the ends of the inner side harness and of the two sections of the harness line of the outer side harness must be released and the tensioning chain must also be released from the locking device. Only then can the wire rope of the inner side harness be pushed around the vehicle wheel, until it once more reaches the front, after which the said connections must be re-established once more in predetermined sequence steps. As previously mentioned, it is also necessary that the tensioning chain be drawn out of the locking device before assembly. And furthermore, for completion of assembly, the tensioning chain must once again be threaded through the locking device before tightening of the outer side harness can take place. A substantial amount of manual dexterity is necessary and a large number of manipulations that have to be performed cannot be done at all with, for example, bulky gloves such as fur-lined gloves or the like. In addition, the establishment of the said connections is almost impossible in unfavourable lighting conditions without the use of an additional light source. In order to avoid excessive strain on the expansion members caused by excessive pulling of the free end of the tensioning chain, there is applied in the interior of spiral springs which form the expansion members a chin section which hangs loosely in the relaxed condition of the spiral springs, and which only permits extension of the spiral springs up to a predetermined limit. If the expansion members, however, are not tensioned to their load limit, undesirable noise can develop inside each spiral spring through the relaxed chain section present within the spring. Apart from that, undesired vibrations may arise as a result of the dynamic stresses induced in the chains during driving because of the spiral springs used. These vibrations also intensify the running noise of the anti-skid chain. Furthermore, the spiral springs lie against the outer side wall of the vehicle tire which can give rise to undesirable abrasion of the tire.